Imaging lens

ABSTRACT

A compact high-resolution imaging lens which provides a wide field of view of 80 degrees or more and corrects various aberrations properly. Designed for a solid-state image sensor, the imaging lens includes constituent lenses arranged in the following order from an object side to an image side: a first positive (refractive power) lens having a convex object-side surface; a second negative lens having a concave image-side surface; a third positive lens as a double-sided aspheric lens having a convex object-side surface; a fourth positive lens having a convex image-side surface; a fifth lens as a double-sided aspheric lens having a concave image-side surface; and a sixth negative lens having a concave image-side surface. The image-side surface of the sixth lens has an aspheric shape with a pole-change point in a position off an optical axis.

This application is a continuation of U.S. application Ser. No.14/287,288 filed on May 27, 2014, which is based on and claims priorityof Japanese patent application No. 2013-116152 filed on May 31, 2013,and Japanese patent application No. 2014-035806 filed on Feb. 26, 2014,the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to imaging lenses which form an image ofan object on a solid-state image sensor such as a CCD sensor or a C-MOSsensor used in a compact image pickup device. More particularly, theinvention relates to imaging lenses which are built in image pickupdevices mounted in highly functional products such as smart TVs and 4KTVs, information terminals such as game consoles and PCs, and mobileterminals such as smart phones, mobile phones and PDAs (Personal DigitalAssistants).

Description of the Related Art

In recent years, highly functional products, such as a smart TV as a TVwith a personal computer function and a 4K TV as a TV with four timeshigher resolution than a full high-definition TV, have been attractingattention. In smart TVs, the tendency toward products which are not onlyhighly functional but also multifunctional is growing, so the smart TVmarket is expected to expand in the future. Some smart TVs provide afunction to take video and still images through a built-in image pickupdevice and transmit the images through a communication network. Thisfunction can be used in various application fields: for example, a videophone and a high-precision people meter based on face recognitiontechnology, and other various products such as a security product and apet monitoring product which have a moving object detection function.Also, due to its high resolution, a 4K TV can reproduce an image whichis so realistic as if the object were there. With the spread of smartTVs or similar products, these functions are expected to be more popularthan before. On the other hand, digital photo frames with a camerafunction have been recently introduced into the market. Thus, the marketrelated to cameras is expected to expand.

In communications over a video phone, for example, in a TV conference inwhich several people participate, the facial expression of the speakerand the surrounding scene are important information. In addition, whenface recognition technology is used to recognize the faces of humanbeings or animals, image recognition should be highly accurate. Theimaging lens used in such a high resolution product is required to havea compact lens system which provides high resolution, a wide field ofview and high brightness.

However, in the conventional techniques, it is difficult to meet thisdemand satisfactorily. For example, the image pickup device used in ahighly functional product such as a smart TV is assumed to adopt arelatively large image sensor suitable for high resolution images. If aconventional imaging lens is used in a large image sensor, since itsoptical system should be large, the following problem arises thatvarious aberrations become more serious and it is very difficult todeliver the same level of high optical performance as in a small imagesensor. In addition, when the lens is designed to provide a wide fieldof view, correction of aberrations may be very difficult, particularlyin the peripheral area, regardless of image sensor size and it may beimpossible to deliver satisfactory optical performance.

As imaging lenses for use in an apparatus with an image pickup device,the imaging lenses described in Patent Document 1 to Patent Document 3are known.

JP-A-2010-262270 (Patent Document 1) discloses an imaging lens whichincludes, in order from an object side, a first lens with positiverefractive power having a convex shape on the object-side surface nearan optical axis, a second lens with negative refractive power, a thirdlens with positive refractive power having a concave shape on animage-side surface near the optical axis, a fourth lens with positiverefractive power having a convex shape on the image-side surface nearthe optical axis, and a fifth lens with negative refractive power nearthe optical axis. The imaging lens described in Patent Document 1includes five constituent lenses, each of which is optimized to deliverhigh performance.

JP-A-2012-155223 (Patent Document 2) discloses an imaging lens whichincludes, in order from an object side, a first lens group with positiverefractive power, a second lens group with negative refractive power, athird lens group with positive refractive power, a fourth lens groupwith negative refractive power, a fifth lens group with positiverefractive power, and a sixth lens group with negative refractive power.In the imaging lens described in Patent Document 2, the lensconfiguration of the optical system is concentric with an aperture stopso as to suppress astigmatism and coma aberrations and provide a widerfield of view.

US 2012/0188654 A1 (Patent Document 3) discloses an imaging lens whichincludes, in order from an object side, a first lens with positiverefractive power having a convex surface on the object side, a secondlens, a third lens, a fourth lens, a fifth lens, and a sixth lens as adouble-sided aspheric lens having a concave surface on an image side, inwhich the sixth lens has at least one pole-change point on itsimage-side surface. The imaging lens described in Patent Document 3 isproposed as a compact imaging lens in which the sum of the refractivepowers of the fifth lens and the sixth lens in the overall opticalsystem is within an adequate range to ensure low manufacturing errorsensitivity and sufficient telecentricity.

The imaging lens described in Patent Document 1 has a lens system whichprovides high brightness with an F-value of 2.0 and a relatively widefield of view with a half field of view of about 38 degrees. However, itcannot meet the recent demand for a wider field of view. Also, for usein a large image sensor, various aberrations must be further suppressed.However, if an imaging lens uses five constituent lenses, its ability tocorrect aberrations is limited and it is difficult to apply the imaginglens to a higher resolution apparatus as mentioned above.

The imaging lens described in Patent Document 2 provides relatively highbrightness with an F-value of about 2.3 and can correct aberrationsproperly. However, its half field of view is about 33 degrees, whichmeans that it cannot meet the demand for a wide field of viewsatisfactorily. Also, if the lens configuration described in PatentDocument 2 is employed to provide a wide field of view, correction ofaberrations will be difficult, particularly in the peripheral area andhigh optical performance cannot be delivered.

The imaging lens described in Patent Document 3 includes six constituentlenses and corrects aberrations properly, offering a relatively compactlens system. Its half field of view is relatively wide at about 37degrees. However, the F-value is in the range from 2.8 to 3.2,suggesting that its brightness is not sufficient. In this imaging lens,it is difficult to address the problem of aberrations in the peripheralarea so as to achieve a low F-value and a half field of view of 40degrees or more.

As mentioned above, in the conventional techniques, it is difficult toprovide a sufficiently wide field of view while ensuring compactness,and meet the demand for brightness and high resolution. Also, for use ina large image sensor, it is difficult to deliver the same level of highoptical performance as in a conventional small image sensor.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problem and anobject thereof is to provide a high-brightness compact imaging lenswhich delivers higher optical performance than conventional imaginglenses, provides a wide field of view and can correct variousaberrations properly when it is used not only in a conventional smallimage sensor but also in a large image sensor.

Here, a “compact” imaging lens means an imaging lens in which the totaltrack length is shorter than the length of the diagonal of the effectiveimage plane of the image sensor and a “wide field of view” refers to afield of view of 80 degrees or more. The length of the diagonal of theeffective image plane of the image sensor is considered to be the sameas the diameter of the effective image circle whose radius is themaximum image height, namely the vertical height from an optical axis tothe position where a light ray incident on the imaging lens at a maximumfield of view enters the image plane.

According to one aspect of the present invention, there is provided animaging lens for a solid-state image sensor in which constituent lensesare arranged in the following order from an object side to an imageside: a first lens with positive refractive power having a convexsurface on the object side; a second lens with negative refractive powerhaving a concave surface on the image side; a third lens with positiverefractive power as a double-sided aspheric lens having a convex surfaceon the object side; a fourth lens with positive refractive power havinga convex surface on the image side; a fifth lens as a double-sidedaspheric lens having a concave surface on the image side; and a sixthlens with negative refractive power having a concave surface on theimage side. The image-side surface of the sixth lens has an asphericshape with a pole-change point in a position off the optical axis.

In the imaging lens with the above configuration, it is possible toprovide a focal length to increase the value of ih/f (to 0.87 or more)while suppressing aberrations. In fact, the values of ih/f are 0.87 to1.04. On the other hand, the values of ih/f in Patent Document 2 are0.65 to 0.71 and those in Patent Document 3 are 0.60 to 0.74. ih denotesa maximum image height and f denotes the focal length of the overalloptical system of the imaging lens. ih and f are parameters whichdetermine the field of view.

The above imaging lens is a telephoto lens which includes a lens groupwith composite positive refractive power composed of the first, second,third, and fourth lenses and a lens group with composite negativerefractive power composed of the fifth and sixth lenses in order toachieve a short total track length.

The first lens is a lens with positive refractive power having a convexsurface on the object side and its refractive power is relatively strongamong the constituent lenses of the imaging lens. It has a biconvexshape in which the curvature radius of the object-side surface issmaller than the curvature radius of the image-side surface, and itspositive refractive power is adequately distributed to the both surfacesso as to suppress spherical aberrations and provide relatively strongrefractive power for compactness of the imaging lens. Alternatively, theimage-side surface of the first lens may be concave and in that case, itis desirable that the curvature radius of the image-side surface belarger than the curvature radius of the object-side surface to theextent that the refractive power is not too low and sphericalaberrations do not increase.

The second lens is a lens with negative refractive power having aconcave surface on the image side which corrects spherical aberrationsand chromatic aberrations properly.

The third lens is a lens having a convex surface on the object side withrelatively weak positive refractive power among the constituent lensesof the imaging lens. It gives additional positive refractive power tothe overall optical system of the imaging lens, thereby contributing toa shorter overall focal length and a wider field of view. Also, due toits aspheric surfaces on the both sides, it mainly corrects astigmatismand coma aberrations properly.

The fourth lens is a lens with positive refractive power having a convexsurface on the image side, and its positive refractive power isrelatively strong among the constituent lenses of the imaging lens. Itsrefractive power is balanced with the positive refractive power of thefirst lens, contributing to the compactness of the imaging lens.

The fifth lens is a double-sided aspheric lens having a concave surfaceon the image side, and due to the aspheric surfaces on the both sides,it properly corrects chromatic aberrations which occur on the third andfourth lenses and contributes to high resolution.

The sixth lens is a lens with negative refractive power having a concavesurface on the image side, making it easy to ensure an adequate backfocus. Due to the aspheric image-side surface with a pole-change pointin a position off the optical axis, the negative refractive power of theimage-side surface gradually decreases and changes to positiverefractive power in the lens peripheral portion. This aspheric shape iseffective mainly in correcting distortion and field curvature andcontrolling the angle of a light ray incident on the image sensor.

As for lens surface shapes, the terms “convex surface” and “concavesurface” are used to express the shape of a paraxial surface (surfacenear the optical axis). A “pole-change point” here means a point on anaspheric surface at which a tangential plane intersects the optical axisperpendicularly.

Preferably, in the imaging lens according to the present invention, thefifth lens is a meniscus lens with negative refractive power having aconcave surface on the image side in which each of the object-sidesurface and the image-side surface has an aspheric shape with apole-change point in a position off the optical axis.

Since the fifth lens has negative refractive power, it can properlycorrect spherical aberrations and chromatic aberrations which occur onthe third and fourth lenses. Among the six constituent lenses, thepresence of the fifth lens with negative refractive power in addition tothe second lens with negative refractive power makes it easy to correctspherical aberrations and chromatic aberrations properly. Since thefifth lens is a meniscus lens having a convex surface on the image sideand each of its object-side and image-side surfaces has an asphericshape with a pole-change point in a position off the optical axis, itcan correct astigmatism and coma aberrations properly and improveoff-axial optical performance and control the angle of a light rayincident on the image sensor. Such aspheric surfaces of the fifth lensmake it easy to make the normal line angle of the aspheric shape of theperipheral portion of the sixth lens, located nearest to the imageplane, an obtuse angle. This is effective in lowering manufacturingerror sensitivity of the sixth lens and suppressing ghost phenomenacaused by internal reflection of the sixth lens.

Preferably, in the imaging lens according to the present invention, thesixth lens is a meniscus lens having a concave surface on the image sidein which the object-side surface has an aspheric shape with apole-change point in a position off the optical axis.

Since the sixth lens is a meniscus lens having a concave surface on theimage side and its object-side surface also has an aspheric shape with apole-change point in a position off the optical axis, it can performfinal correction of field curvature and final control of the angle of alight ray incident on the image sensor without impairing theabove-mentioned aberration correction effect of the fifth lens. In orderto ensure compactness, it is desirable that the aspheric surface be soshaped as to keep the change in the amount of sag small.

Alternatively, the fifth lens may have positive refractive power. Inthat case, if the positive refractive power of the fifth lens is weak sothat the composite refractive power of the fifth and sixth lenses isnegative and positive refractive power is adequately distributed amongthe first, third, and fourth lenses, it will be easier to shorten thetotal track length while suppressing various aberrations.

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (1) below:0.55<f1/f<1.7  (1)

where f denotes the focal length of the overall optical system of theimaging lens, and f1 denotes the focal length of the first lens.

The conditional expression (1) defines an adequate range for the ratioof the focal length of the first lens to the focal length of the overalloptical system of the imaging lens and indicates a condition to achievecompactness of the imaging lens and correct spherical aberrations andcoma aberrations properly. If the value is above the upper limit of theconditional expression (1), the positive refractive power of the firstlens would be too weak to achieve compactness of the imaging lens. Onthe other hand, if the value is below the lower limit of the conditionalexpression (1), the positive refractive power of the first lens would betoo strong to correct spherical aberrations and coma aberrationsproperly.

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (2) below:−2.3<f2/f<−0.8  (2)

where f denotes the focal length of the overall optical system of theimaging lens, and f2 denotes the focal length of the second lens.

The conditional expression (2) defines an adequate range for the ratioof the focal length of the second lens to the focal length of theoverall optical system of the imaging lens and indicates a condition toachieve compactness of the imaging lens and correct chromaticaberrations properly. If the value is above the upper limit of theconditional expression (2), the negative refractive power of the secondlens would be too strong to achieve compactness of the imaging lens.Also, axial and off-axial chromatic aberrations would be excessivelycorrected (chromatic aberration at short wavelengths increases in thepositive direction with respect to chromatic aberration at the referencewavelength), making it difficult to deliver high imaging performance. Onthe other hand, if the value is below the lower limit of the conditionalexpression (2), the negative refractive power of the second lens wouldbe too weak to correct axial and off-axial chromatic aberrationsproperly (chromatic aberration at short wavelengths increases in thenegative direction with respect to chromatic aberration at the referencewavelength). In this case as well, it would be difficult to deliver highimaging performance.

Preferably, the imaging lens according to the present inventionsatisfies conditional expressions (3) and (4) below:45<νd1<80  (3)20<νd2<40  (4)

where νd1 denotes the Abbe number of the first lens at d-ray, and νd2denotes the Abbe number of the second lens at d-ray.

The conditional expressions (3) and (4) define adequate ranges for theAbbe numbers of the first and second lenses respectively and indicateconditions to correct chromatic aberrations properly. If the value isbelow the lower limit of the conditional expression (3) or the value isabove the upper limit of the conditional expression (4), the differencein dispersion value between the first and second lenses would besmaller, making it impossible to correct chromatic aberrations properly.If the value is above the upper limit of the conditional expression (3)or the value is below the lower limit of the conditional expression (4),the balance between axial chromatic aberration and chromatic aberrationof magnification would worsen, resulting in deterioration in opticalperformance in the peripheral portion.

Preferably, the imaging lens according to the present inventionsatisfies conditional expressions (5) to (8) below:50<νd3<75  (5)50<νd4<75  (6)20<νd5<40  (7)50<νd6<75  (8)

where νd3 denotes the Abbe number of the third lens at d-ray, νd4denotes the Abbe number of the fourth lens at d-ray, νd5 denotes theAbbe number of the fifth lens at d-ray, and νd6 denotes the Abbe numberof the sixth lens at d-ray.

The conditional expressions (5), (6), (7) and (8) define adequate rangesfor the Abbe numbers of the third, fourth, fifth, and sixth lensesrespectively and indicate conditions to correct chromatic aberrationsproperly. These conditional expressions suggest that the third, fourth,and sixth lenses are made of low-dispersion material and the fifth lensis made of high-dispersion material. The lenses of low-dispersionmaterial and the lens of high-dispersion material are alternatelyarranged so that axial chromatic aberrations and chromatic aberrationsof magnification can be corrected more properly.

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (10) below:TTL/f<1.6  (10)

where f denotes the focal length of the overall optical system of theimaging lens, and TTL denotes the distance on the optical axis from theobject-side surface of an optical element located nearest to the objectto the image plane without a filter, etc.

The conditional expression (10) indicates a condition to make theimaging lens compact. If the value is above the upper limit of theconditional expression (10), the image-side principal point of theimaging lens would shift toward the object too much and the total tracklength would become too long, making it difficult to achievecompactness.

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (9) below:0.65<Σd/TTL<0.90  (9)

where Σd denotes the distance on the optical axis from the object-sidesurface of the first lens to the image-side surface of the sixth lens,and TTL denotes the distance on the optical axis from the object-sidesurface of an optical element located nearest to the object to the imageplane without a filter, etc.

The conditional expression (9) indicates a condition to shorten thetotal track length and correct aberrations properly. If the value isabove the upper limit of the conditional expression (9), the back focuswould be too short and it would be difficult to obtain space for afilter or the like and also it would be difficult to control the angleof a light ray incident on the image sensor within an adequate range. Onthe other hand, if the value is below the lower limit of the conditionalexpression (9), it would be difficult for each constituent lens of theimaging lens to have the required thickness. In addition, the distancebetween constituent lenses would be smaller, which might restrict thefreedom of aspheric shape design. As a consequence, it would bedifficult to deliver high optical performance.

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (11) below:0.8<ih/f<1.2  (11)

where f denotes the focal length of the overall optical system of theimaging lens, and ih denotes the maximum image height.

The conditional expression (11) defines an adequate range for the ratioof maximum image height to the focal length of the overall opticalsystem of the imaging lens and indicates a condition to provide a widefield of view and deliver high imaging performance. If the value isabove the upper limit of the conditional expression (11), the field ofview would be too wide to correct aberrations in the peripheral portionproperly, leading to deterioration in optical performance, particularlyin the peripheral area of the image. On the other hand, if the value isbelow the lower limit of the conditional expression (11), the focallength of the overall optical system of the imaging lens would be toolong to achieve compactness, offering a disadvantage in providing a widefield of view.

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (12) below:1.3<f3/f<7.0  (12)

where f3 denotes the focal length of the third lens, and f denotes thefocal length of the overall optical system of the imaging lens.

The conditional expression (12) defines an adequate range for the ratioof the focal length of the third lens to the focal length of the overalloptical system of the imaging lens, and indicates a condition to achievecompactness and correct various aberrations properly. If the value isabove the upper limit of the conditional expression (12), the positiverefractive power of the third lens would be too weak to provide a widefield of view. On the other hand, if the value is below the lower limitof the conditional expression (12), the positive refractive power of thethird lens would be too strong to correct spherical aberrations, thougha wide field of view and compactness may be achieved easily. When theconditional expression (12) is satisfied, the balance of thedistribution of positive refractive power in the overall optical systemand the balance of the aberration correction can be achieved easily.

Preferably, the imaging lens according to the present inventionsatisfies conditional expressions (13) and (14) below:0.5<f1234/f<7.5  (13)−1.2<f56/f<−0.5  (14)

where f1234 denotes the composite focal length of the first to fourthlenses, f56 denotes the composite focal length of the fifth and sixthlenses, and f denotes the focal length of the overall optical system ofthe imaging lens.

The conditional expression (13) defines an adequate range for the ratioof the composite positive focal length of the first to fourth lenses tothe focal length of the overall optical system of the imaging lens, andthe conditional expression (14) defines an adequate range for the ratioof the composite negative focal length of the fifth and sixth lenses tothe focal length of the overall optical system of the imaging lens. Whenthese conditional expressions are satisfied, the telephoto ability isenhanced and increase in total track length is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the general configuration of animaging lens in Example 1;

FIG. 2 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 1;

FIG. 3 is a schematic view showing the general configuration of animaging lens in Example 2;

FIG. 4 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 2;

FIG. 5 is a schematic view showing the general configuration of animaging lens in Example 3;

FIG. 6 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 3;

FIG. 7 is a schematic view showing the general configuration of animaging lens in Example 4;

FIG. 8 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 4;

FIG. 9 is a schematic view showing the general configuration of animaging lens in Example 5;

FIG. 10 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 5;

FIG. 11 is a schematic view showing the general configuration of animaging lens in Example 6;

FIG. 12 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 6;

FIG. 13 is a schematic view showing the general configuration of animaging lens in Example 7;

FIG. 14 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 7;

FIG. 15 is a schematic view showing the general configuration of animaging lens in Example 8;

FIG. 16 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 8;

FIG. 17 is a schematic view showing the general configuration of animaging lens in Example 9;

FIG. 18 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 9;

FIG. 19 is a schematic view showing the general configuration of animaging lens in Example 10;

FIG. 20 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 10;

FIG. 21 is a schematic view showing the general configuration of animaging lens in Example 11; and

FIG. 22 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the preferred embodiment of the present invention will bedescribed in detail referring to the accompanying drawings.

FIGS. 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, and 21 are schematic viewsshowing the general configurations of the imaging lenses according toExamples 1 to 11 of this embodiment respectively. Since all theseexamples have the same basic configuration, the general configuration ofan imaging lens according to this embodiment is explained belowreferring to the schematic view of Example 1.

As shown in FIG. 1, the imaging lens according to this embodimentincludes an aperture stop ST, a first lens L1 with positive refractivepower, a second lens L2 with negative refractive power, a third lens L3with positive refractive power, a fourth lens L4 with positiverefractive power, a fifth lens L5 with negative refractive power, and asixth lens L6 with negative refractive power which are arranged in orderfrom an object side to an image side.

A filter IR is located between the sixth lens L6 and an image plane IM.This filter IR is omissible.

In the above imaging lens composed of six constituent lenses, the firstlens L1 is a biconvex lens in which the object-side surface andimage-side surface are both convex. The first lens L1 has only to have aconvex object-side surface, and thus it may have a concave image-sidesurface. In Examples 8 and 11, the first lens L1 is a meniscus lens witha convex object-side surface.

The second lens L2 is a meniscus lens in which the object-side surfaceis convex and the image-side surface is concave. The second lens L2 hasonly to have a concave image-side surface, and thus it may have aconcave object-side surface. In Example 8, the second lens L2 is abiconcave lens.

The third lens L3 is a meniscus lens in which the object-side surface isconvex and the image-side surface is concave. The third lens L3 has onlyto have weak positive refractive power to correct aberrations andprovide a wide field of view, and is thus not limited to the aboveshape. In Examples 5 to 9 and Example 11, the third lens L3 is abiconvex lens.

The fourth lens L4 is a meniscus lens having positive refractive power,in which the object-side surface is concave and the image-side surfaceis convex. The both surfaces of the fourth lens L4 have such an asphericshape that the positive refractive power decreases toward the lensperipheral portion. Due to the weak positive refractive power in theperipheral portion, the lens mainly corrects astigmatism and fieldcurvature properly.

The fifth lens L5 is a meniscus lens in which the object-side surface isconvex and the image-side surface is concave. The object-side surfaceand image-side surface have an aspheric shape with a pole-change pointin a position off the optical axis X. The refractive power of the fifthlens L5 should be such that the composite refractive power of the fifthlens L5 and the sixth lens L6 is negative. Therefore, for example, itmay have weak positive refractive power. In Example 9, the fifth lens L5has positive refractive power. The shape of the fifth lens L5 is notlimited to a meniscus shape, and instead it may be a biconcave lens asshown in Example 10.

The sixth lens L6 is a meniscus lens in which the object-side surface isconvex and the image-side surface is concave. The object-side surfaceand the image-side surface have an aspheric shape with a pole-changepoint in a position off the optical axis X. The lens is shaped so thatit has negative refractive power near the optical axis X and thenegative refractive power gradually decreases and changes to positiverefractive power in the peripheral portion. The shape of the sixth lensL6 is not limited to a meniscus shape, and instead it may be a biconcavelens as shown in Example 9.

In the imaging lens according to this embodiment, the first lens L1, thesecond lens L2, the third lens L3, the fourth lens L4, the fifth lensL5, and the sixth lens L6 are all made of plastic material so that themanufacturing process is simplified and the imaging lens can bemass-produced at low cost. All the constituent lenses have adequateaspheric surfaces on both the object and image sides to correct variousaberrations more properly.

The material of the lenses is not limited to plastic material. Glassmaterial may be used to achieve higher performance. It is preferablethat all the lens surfaces be aspheric. However, according to therequired performance, the lens surface may be spherical from theviewpoint of manufacturing ease.

The imaging lens according to this embodiment brings about favorableeffects when it satisfies the following conditional expressions (1) to(14):0.55<f1/f<1.7  (1)−2.3<f2/f<−0.8  (2)45<νd1<80  (3)20<νd2<40  (4)50<νd3<75  (5)50<νd4<75  (6)20<νd5<40  (7)50<νd6<75  (8)0.65<Σd/TTL<0.90  (9)TTL/f<1.6  (10)0.8<ih/f<1.2  (11)1.3<f3/f<7.0  (12)0.5<f1234/f<7.5  (13)−1.2<f56/f<−0.5  (14)

where

-   -   f: focal length of the overall optical system of the imaging        lens    -   f1: focal length of the first lens L1    -   f2: focal length of the second lens L2    -   f3: focal length of the third lens L3    -   νd1: Abbe number of the first lens L1 at d-ray    -   νd2: Abbe number of the second lens L2 at d-ray    -   νd3: Abbe number of the third lens L3 at d-ray    -   νd4: Abbe number of the fourth lens L4 at d-ray    -   νd5: Abbe number of the fifth lens L5 at d-ray    -   νd6: Abbe number of the sixth lens L6 at d-ray    -   TTL: distance on the optical axis X from the object-side surface        of an optical element located nearest to the object to the image        plane IM without the filter IR, etc.    -   Σd: distance on the optical axis X from the object-side surface        of the first lens L1 to the image-side surface of the sixth lens        L6    -   ih: maximum image height    -   f1234: composite focal length of the first lens L1 to the fourth        lens L4    -   f56: composite focal length of the fifth lens L5 and the sixth        lens L6.

The imaging lens according to this embodiment brings about morefavorable effects when it satisfies the following conditionalexpressions (1a) to (14a):0.6<f1/f<1.5  (1a)−2.1<f2/f<−0.9  (2a)45<νd1<70  (3a)20<νd2<30  (4a)50<νd3<65  (5a)50<νd4<65  (6a)20<νd5<30  (7a)50<νd6<65  (8a)0.70<Σd/TTL<0.90  (9a)TTL/f<1.55  (10a)0.8<ih/f<1.1  (11a)1.4<f3/f<6.4  (12a)0.6<f1234/f<7.0  (13a)−1.0<f56/f<−0.5  (14a)

The signs in the conditional expressions are the same as described inthe preceding paragraph.

The imaging lens according to this embodiment brings about further morefavorable effects when it satisfies the following conditionalexpressions (1b) to (14b):0.71≦f1/f≦1.42  (1b)-1.9≦f2/f≦−1.07  (2b)50<νd1<70  (3b)22<νd2<28  (4b)53<νd3<60  (5b)53<νd4<60  (6b)22<νd5<28  (7b)50<νd6<60  (8b)0.76≦Σd/TTL≦0.86  (9b)TTL/f1.43  (10b)0.87≦ih/f≦1.04  (11b)1.59≦f3/f≦5.83  (12b)0.67≦f1234/f≦6.29  (13b)−0.94≦f56/f≦−0.63  (14b)

The signs in the conditional expressions are the same as described inthe preceding paragraph.

In this embodiment, the aspheric shapes of the aspheric lens surfacesare expressed by the following equation 1, where Z denotes an axis inthe optical axis direction, H denotes a height perpendicular to theoptical axis, k denotes a conic constant, and A4, A6, A8, A10, A12, A14,and A16 denote aspheric surface coefficients.

$\begin{matrix}{Z = {\frac{\frac{H^{2}}{R}}{1 + \sqrt{1 - {\left( {k + 1} \right)\frac{H^{2}}{R^{2}}}}} + {A_{4}H^{4}} + {A_{6}H^{6}} + {A_{8}H^{8}} + {A_{10}H^{10}} + {A_{12}H^{12}} + {A_{14}H^{14}} + {A_{16}H^{16}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Next, the imaging lenses in examples according to this embodiment willbe explained. In each example, f denotes the focal length of the overalloptical system of the imaging lens, Fno denotes an F-number, ω denotes ahalf field of view, and ih denotes a maximum image height. i denotes asurface number counted from the object side, r denotes a curvatureradius, d denotes the distance between lens surfaces on the optical axisX (surface distance), Nd denotes a refractive index at d-ray (referencewavelength), and νd denotes an Abbe number at d-ray. As for asphericsurfaces, an asterisk (*) after surface number i indicates that thesurface concerned is an aspheric surface.

EXAMPLE 1

The basic lens data of Example 1 is shown below in Table 1.

TABLE 1 Example 1 in mm f = 8.881 Fno = 2.40 ω(°) = 41.3 ih = 7.902Surface Data Curvature Surface Refractive Abbe Surface No. i Radius rDistance d Index Nd Number vd (Object Surface) Infinity Infinity  1(Stop) Infinity −0.355  2* 4.275 1.484 1.5438 55.57  3* −15.055 0.040 4* 46.740 0.650 1.6142 25.58  5* 5.159 0.913  6* 13.263 0.909 1.534656.16  7* 24.871 0.751  8* −5.600 1.182 1.5346 56.16  9* −2.670 0.07010* 12.443 1.000 1.6142 25.58 11* 6.123 1.330 12* 81.918 1.325 1.534656.16 13* 4.725 0.600 14 Infinity 0.300 1.5670 37.80 15 Infinity 0.746Image Plane Infinity Constituent Lens Data Lens Start Surface FocalLength 1 2 6.293 2 4 −9.498 3 6 51.739 4 8 8.369 5 10 −20.885 6 12−9.435 Composite Focal Length f1234 55.88 f56 −6.17 Aspheric SurfaceData 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface 7thSurface k 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A4−7.869E−04   7.232E−03 4.714E−03 −2.930E−03   −8.477E−03   −7.907E−03  A6 −2.818E−04   −2.373E−03   −2.894E−04   2.261E−03 6.556E−04 1.565E−04A8 4.033E−05 −1.980E−04   −6.140E−04   −4.693E−04   −5.132E−05  1.343E−06 A10 −2.350E−05   4.933E−05 9.916E−05 4.284E−05 5.286E−061.241E−06 A12 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A14 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface13th Surface k 0.000E+00 −2.767E+00   0.000E+00 0.000E+00 0.000E+00−8.787E+00   A4 −7.308E−03   −7.899E−03   1.061E−03 −3.841E−03  −5.323E−03   −3.454E−03   A6 1.093E−03 6.571E−04 −4.490E−04  −2.241E−05   1.227E−04 7.714E−05 A8 1.485E−05 3.600E−05 2.227E−056.595E−07 1.826E−06 −2.206E−06   A10 −4.030E−06   −1.909E−06  −1.009E−06   1.180E−09 −7.680E−08   4.482E−08 A12 0.000E+00 −1.356E−07  2.131E−08 −2.170E−10   6.370E−10 −4.674E−10   A14 0.000E+00 5.080E−090.000E+00 1.563E−12 −4.811E−12   2.973E−12 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 8.557E−14 0.000E+00

As shown in Table 12, the imaging lens in Example 1 satisfies all theconditional expressions (1) to (14).

FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 1. The spherical aberration diagramshows the amount of aberration at wavelengths of F-ray (486 nm), d-ray(588 nm), and C-ray (656 nm). The astigmatism diagram shows the amountof aberration on sagittal image surface S and the amount of aberrationon tangential image surface T (the same is true for FIGS. 4, 6, 8, 10,12, 14, 16, 18, 20, and 22). As shown in FIG. 2, each aberration isproperly corrected.

The imaging lens provides a wide field of view of about 80 degrees andhigh brightness with an F-value of about 2.4. The ratio of total tracklength TTL to maximum image height ih (TTL/2ih) is 0.71, which suggeststhat it achieves compactness though it uses six constituent lenses.

EXAMPLE 2

The basic lens data of Example 2 is shown below in Table 2.

TABLE 2 Example 2 in mm f = 6.764 Fno = 2.40 ω(°) = 41.2 ih = 5.992Surface Data Curvature Surface Refractive Abbe Surface No. i Radius rDistance d Index Nd Number vd (Object Surface) Infinity Infinity  1(Stop) Infinity −0.185  2* 4.053 1.066 1.5438 55.57  3* −8.816 0.101  4*35.089 0.500 1.6142 25.58  5* 4.155 0.648  6* 8.544 0.710 1.5346 56.16 7* 29.084 0.609  8* −4.038 1.305 1.5346 56.16  9* −2.016 0.053 10*11.903 0.790 1.6142 25.58 11* 5.003 0.606 12* 6.366 1.097 1.5346 56.1613* 2.525 0.600 14 Infinity 0.300 1.5670 37.80 15 Infinity 0.850 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 25.259 2 4 −7.720 3 6 22.360 4 8 6.148 5 10 −14.692 6 12 −8.694 CompositeFocal Length f1234 17.09 f56 −5.12 Aspheric Surface Data 2nd Surface 3rdSurface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A4 −2.806E−03  1.014E−02 3.547E−03 −1.407E−02   −1.733E−02   −8.408E−03   A6−1.408E−03   −6.129E−03   6.567E−04 7.185E−03 7.447E−04 −5.976E−04   A81.483E−04 −8.568E−04   −2.831E−03   −2.432E−03   −4.760E−04  −1.198E−04   A10 −2.127E−04   2.706E−04 6.580E−04 3.266E−04 1.354E−046.402E−05 A12 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A14 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface13th Surface k 0.000E+00 −2.706E+00   0.000E+00 0.000E+00 0.000E+00−5.182E+00   A4 2.757E−04 −1.128E−02   1.201E−04 −6.202E−03  −1.439E−02   −8.058E−03   A6 2.427E−03 1.653E−03 −6.291E−04  −1.038E−04   5.183E−04 4.112E−04 A8 −2.805E−05   1.199E−04 2.665E−052.933E−06 7.560E−06 −1.829E−05   A10 −1.424E−05   −1.105E−05  −3.859E−06   −1.143E−07   −8.600E−07   4.749E−07 A12 0.000E+00−5.852E−07   1.975E−07 1.777E−08 1.326E−08 −6.914E−09   A14 0.000E+002.008E−08 0.000E+00 −6.163E−10   1.495E−10 7.295E−11 A16 0.000E+000.000E+00 0.000E+00 0.000E+00 −3.814E−12   0.000E+00

As shown in Table 12, the imaging lens in Example 2 satisfies all theconditional expressions (1) to (14).

FIG. 4 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 2. As shown in FIG. 4, eachaberration is corrected properly.

The imaging lens provides a wide field of view of about 80 degrees andhigh brightness with an F-value of about 2.4. The ratio of total tracklength TTL to maximum image height ih (TTL/2ih) is 0.76, which suggeststhat it achieves compactness though it uses six constituent lenses.

EXAMPLE 3

The basic lens data of Example 3 is shown below in Table 3.

TABLE 3 Example 3 in mm f = 6.765 Fno = 2.40 ω(°) = 41.2 ih = 5.992Surface Data Curvature Surface Refractive Abbe Surface No. i Radius rDistance d Index Nd Number vd (Object Surface) Infinity Infinity  1(Stop) Infinity −0.185  2* 4.045 1.107 1.5438 55.57  3* −9.409 0.092  4*27.849 0.500 1.6142 25.58  5* 4.146 0.664  6* 9.263 0.710 1.5346 56.16 7* 37.916 0.583  8* −4.000 1.320 1.5346 56.16  9* −2.016 0.053 10*12.018 0.790 1.6142 25.58 11* 5.129 0.626 12* 5.903 1.045 1.5346 56.1613* 2.440 0.700 14 Infinity 0.300 1.5640 51.30 15 Infinity 0.778 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 25.357 2 4 −7.994 3 6 22.730 4 8 6.172 5 10 −15.234 6 12 −8.692 CompositeFocal Length f1234 16.97 f56 −5.20 Aspheric Surface Data 2nd Surface 3rdSurface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A4 −2.321E−03  1.017E−02 2.905E−03 −1.319E−02   −1.643E−02   −8.716E−03   A6−1.169E−03   −5.693E−03   7.463E−04 6.718E−03 7.583E−04 −4.328E−04   A81.335E−04 −9.045E−04   −2.813E−03   −2.270E−03   −4.596E−04  −1.578E−04   A10 −1.753E−04   2.848E−04 6.371E−04 3.063E−04 1.284E−046.544E−05 A12 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A14 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface13th Surface k 0.000E+00 −2.719E+00   0.000E+00 0.000E+00 0.000E+00−4.942E+00   A4 −7.353E−05   −1.185E−02   1.516E−04 −5.996E−03  −1.536E−02   −8.186E−03   A6 2.341E−03 1.710E−03 −6.113E−04   −1.191E−04   5.610E−04 4.145E−04 A8 −2.067E−05   9.533E−05 2.562E−05 4.170E−067.604E−06 −1.769E−05   A10 −1.261E−05   −1.102E−05   −3.599E−06  −9.897E−08   −9.052E−07   4.691E−07 A12 0.000E+00 −3.537E−07   1.878E−071.972E−08 1.218E−08 −8.036E−09   A14 0.000E+00 1.675E−08 0.000E+00−7.065E−10   2.204E−10 9.571E−11 A16 0.000E+00 0.000E+00 0.000E+000.000E+00 −4.665E−12   0.000E+00

As shown in Table 12, the imaging lens in Example 3 satisfies all theconditional expressions (1) to (14).

FIG. 6 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 3. As shown in FIG. 6, eachaberration is corrected properly.

In addition, the imaging lens provides a wide field of view of about 80degrees and high brightness with an F-value of about 2.4. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.76,which suggests that it achieves compactness though it uses sixconstituent lenses.

EXAMPLE 4

The basic lens data of Example 4 is shown below in Table 4.

TABLE 4 Example 4 in mm f = 6.769 Fno = 2.40 ω(°) = 41.1 ih = 5.992Surface Data Curvature Surface Refractive Abbe Surface No. i Radius rDistance d Index Nd Number vd (Object Surface) Infinity Infinity  1(Stop) Infinity −0.185  2* 4.143 1.151 1.5438 55.57  3* −9.595 0.093  4*18.832 0.500 1.6142 25.58  5* 3.909 0.615  6* 9.711 0.743 1.5346 56.16 7* 40.003 0.556  8* −4.000 1.203 1.5346 56.16  9* −2.087 0.053 10*9.339 0.790 1.6142 25.58 11* 4.868 0.741 12* 6.116 1.045 1.5346 56.1613* 2.542 0.700 14 Infinity 0.300 1.5640 51.30 15 Infinity 0.747 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 25.483 2 4 −8.135 3 6 23.783 4 8 6.697 5 10 −17.751 6 12 −9.061 CompositeFocal Length f1234 16.51 f56 −5.69 Aspheric Surface Data 2nd Surface 3rdSurface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A4 −2.210E−03  9.089E−03 1.356E−03 −1.380E−02   −1.697E−02   −9.231E−03   A6−1.344E−03   −6.188E−03   8.687E−05 6.421E−03 1.118E−03 −4.131E−04   A82.102E−04 −8.021E−04   −2.835E−03   −2.270E−03   −4.534E−04  −1.512E−04   A10 −1.834E−04   3.026E−04 6.743E−04 3.122E−04 1.247E−046.095E−05 A12 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A14 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface13th Surface k 0.000E+00 −2.830E+00   0.000E+00 0.000E+00 0.000E+00−4.906E+00   A4 2.258E−03 −1.203E−02   −4.884E−04   −6.509E−03  −1.584E−02   −8.460E−03   A6 2.354E−03 2.072E−03 −6.555E−04  −1.346E−04   5.714E−04 4.204E−04 A8 −2.729E−05   1.060E−04 2.960E−055.936E−06 7.833E−06 −1.818E−05   A10 −1.322E−05   −1.255E−05  −3.614E−06   −1.811E−07   −9.034E−07   4.686E−07 A12 0.000E+00−5.059E−07   1.698E−07 1.739E−08 1.272E−08 −8.040E−09   A14 0.000E+002.375E−08 0.000E+00 −6.431E−10   2.255E−10 1.149E−10 A16 0.000E+000.000E+00 0.000E+00 0.000E+00 −5.148E−12   0.000E+00

As shown in Table 12, the imaging lens in Example 4 satisfies all theconditional expressions (1) to (14).

FIG. 8 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 4. As shown in FIG. 8, eachaberration is corrected properly.

In addition, the imaging lens provides a wide field of view of about 80degrees and high brightness with an F-value of about 2.4. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.76,which suggests that it achieves compactness though it uses sixconstituent lenses.

EXAMPLE 5

The basic lens data of Example 5 is shown below in Table 5.

TABLE 5 Example 5 in mm f = 6.916 Fno = 2.40 ω(°) = 41.4 ih = 5.992Surface Data Curvature Surface Refractive Abbe Surface No. i Radius rDistance d Index Nd Number vd (Object Surface) Infinity Infinity  1(Stop) Infinity −0.21  2* 4.041 1.047 1.5438 55.57  3* −11.886 0.157  4*12.813 0.450 1.6142 25.58  5* 3.618 0.537  6* 11.710 0.805 1.5346 56.16 7* −29.145 0.598  8* −3.161 1.201 1.5346 56.16  9* −1.991 0.045 10*10.872 0.800 1.6142 25.58 11* 5.134 0.552 12* 7.250 1.322 1.5346 56.1613* 2.811 0.700 14 Infinity 0.300 1.5640 51.30 15 Infinity 0.853 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 25.676 2 4 −8.363 3 6 15.733 4 8 7.411 5 10 −16.726 6 12 −9.580 CompositeFocal Length f1234 15.97 f56 −5.73 Aspheric Surface Data 2nd Surface 3rdSurface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A4 −2.474E−03  6.458E−03 −5.685E−04   −1.330E−02   −1.392E−02   −8.317E−03   A6−1.289E−03   −4.960E−03   1.067E−03 5.792E−03 1.054E−03 −1.239E−04   A81.559E−04 −3.592E−04   −2.297E−03   −1.964E−03   −3.285E−04  −1.186E−04   A10 −1.830E−04   9.662E−05 4.656E−04 2.553E−04 1.262E−047.792E−05 A12 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A14 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface13th Surface k 0.000E+00 −2.512E+00   0.000E+00 0.000E+00 0.000E+00−6.302E+00   A4 1.987E−03 −1.044E−02   1.701E−04 −7.304E−03  −1.291E−02   −7.147E−03   A6 3.203E−03 1.924E−03 −9.337E−04  −6.145E−05   5.602E−04 4.007E−04 A8 3.133E−06 6.566E−05 5.271E−054.496E−06 6.196E−06 −1.830E−05   A10 −1.964E−05   −1.041E−05  −3.837E−06   −1.380E−07   −9.614E−07   5.187E−07 A12 0.000E+00−2.908E−07   1.690E−07 2.687E−08 1.342E−08 −8.217E−09   A14 0.000E+00−1.083E−08   0.000E+00 −1.006E−09   3.714E−10 7.249E−11 A16 0.000E+000.000E+00 0.000E+00 0.000E+00 −8.245E−12   0.000E+00

As shown in Table 12, the imaging lens in Example 5 satisfies all theconditional expressions (1) to (14).

FIG. 10 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 5. As shown in FIG. 10,each aberration is corrected properly.

In addition, the imaging lens provides a wide field of view of about 80degrees and high brightness with an F-value of about 2.4. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.77,which suggests that it achieves compactness though it uses sixconstituent lenses.

EXAMPLE 6

The basic lens data of Example 6 is shown below in Table 6.

TABLE 6 Example 6 in mm f = 6.758 Fno = 2.20 ω(°) = 41.2 ih = 5.992Surface Data Curvature Surface Refractive Abbe Surface No. i Radius rDistance d Index Nd Number vd (Object Surface) Infinity Infinity  1(Stop) Infinity −0.25  2* 3.874 1.352 1.5438 55.57  3* −11.427 0.040  4*17.916 0.500 1.6349 23.97  5* 4.274 0.625  6* 22.712 0.768 1.5346 56.16 7* −31.806 0.476  8* −3.954 1.494 1.5346 56.16  9* −1.962 0.053 10*12.215 0.727 1.6349 23.97 11* 5.349 0.510 12* 6.465 1.058 1.5346 56.1613* 2.364 0.700 14 Infinity 0.300 1.5640 51.30 15 Infinity 0.824 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 25.491 2 4 −8.969 3 6 24.906 4 8 5.775 5 10 −15.632 6 12 −7.657 CompositeFocal Length f1234 5.01 f56 −4.86 Aspheric Surface Data 2nd Surface 3rdSurface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A4 −1.317E−03  9.839E−03 −1.327E−03   −1.460E−02   −1.662E−02   −7.424E−03   A6−9.068E−05   −5.052E−03   1.926E−03 6.903E−03 8.641E−05 −8.022E−04   A8−1.295E−04   −7.660E−04   −2.834E−03   −2.194E−03   −6.027E−04  −1.129E−04   A10 −5.232E−05   2.202E−04 5.079E−04 2.788E−04 2.181E−047.240E−05 A12 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A14 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface13th Surface k 0.000E+00 −2.801E+00   0.000E+00 0.000E+00 0.000E+00−5.272E+00   A4 2.467E−03 −1.104E−02   6.824E−04 −5.235E−03  −1.364E−02   −7.376E−03   A6 1.974E−03 1.660E−03 −6.541E−04  −1.079E−04   5.433E−04 4.108E−04 A8 −6.583E−05   4.540E−05 3.554E−052.561E−06 6.508E−06 −1.774E−05   A10 −1.064E−05   −1.187E−05  −3.363E−06   −1.065E−07   −9.038E−07   4.801E−07 A12 0.000E+00−3.618E−08   1.458E−07 2.285E−08 1.326E−08 −8.169E−09   A14 0.000E+001.493E−08 0.000E+00 −7.051E−10   2.524E−10 8.638E−11 A16 0.000E+000.000E+00 0.000E+00 0.000E+00 −5.812E−12   0.000E+00

As shown in Table 12, the imaging lens in Example 6 satisfies all theconditional expressions (1) to (14).

FIG. 12 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 6. As shown in FIG. 12,each aberration is corrected properly.

The imaging lens provides a wide field of view of about 80 degrees andhigh brightness with an F-value of about 2.2. The ratio of total tracklength TTL to maximum image height ih (TTL/2ih) is 0.78, which suggeststhat it achieves compactness though it uses six constituent lenses.

EXAMPLE 7

The basic lens data of Example 7 is shown below in Table 7.

TABLE 7 Example 7 in mm f = 3.344 Fno = 2.20 ω(°) = 40.9 ih = 2.934Surface Data Curvature Surface Refractive Abbe Surface No. i Radius rDistance d Index Nd Number vd (Object Surface) Infinity Infinity  1(Stop) Infinity −0.115  2* 2.121 0.537 1.5438 55.57  3* −5.395 0.024  4*6.363 0.300 1.6349 23.97  5* 1.929 0.297  6* 10.412 0.438 1.5346 56.16 7* −9.392 0.267  8* −1.661 0.696 1.5346 56.16  9* −0.895 0.025 10*7.621 0.360 1.6349 23.97 11* 3.371 0.071 12* 2.819 0.532 1.5346 56.1613* 1.076 0.400 14 Infinity 0.210 1.5640 51.30 15 Infinity 0.566 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 22.872 2 4 −4.477 3 6 9.308 4 8 2.760 5 10 −9.843 6 12 −3.643 CompositeFocal Length f1234 2.41 f56 −2.56 Aspheric Surface Data 2nd Surface 3rdSurface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A4 −1.267E−02  7.401E−02 −2.585E−02   −1.496E−01   −1.198E−01   −4.751E−02   A6−1.747E−02   −1.340E−01   7.707E−02 2.317E−01 8.765E−03 −9.571E−03   A89.840E−03 −1.367E−01   −3.873E−01   −3.189E−01   −7.044E−02  −2.603E−02   A10 −7.903E−02   1.031E−01 2.664E−01 1.591E−01 1.044E−014.047E−02 A12 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A14 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface13th Surface k 0.000E+00 −2.828E+00   0.000E+00 0.000E+00 0.000E+00−5.803E+00   A4 7.918E−02 −1.022E−01   −1.973E−02   −4.227E−02  −1.066E−01   −5.608E−02   A6 6.630E−02 7.339E−02 −1.431E−02  −2.868E−03   1.736E−02 1.313E−02 A8 −1.091E−02   5.185E−03 3.596E−037.170E−04 7.206E−04 −2.402E−03   A10 −3.372E−03   −6.402E−03  −2.139E−03   −3.990E−05   −5.154E−04   2.697E−04 A12 0.000E+00 2.598E−044.259E−04 4.923E−05 3.437E−05 −1.935E−05   A14 0.000E+00 −4.966E−05  0.000E+00 −7.958E−06   2.717E−06 9.100E−07 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 −3.005E−07   0.000E+00

As shown in Table 12, the imaging lens in Example 7 satisfies all theconditional expressions (1) to (14).

FIG. 14 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 7. As shown in FIG. 14,each aberration is corrected properly.

In addition, the imaging lens provides a wide field of view of about 80degrees and high brightness with an F-value of about 2.2. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.79,which suggests that it achieves compactness though it uses sixconstituent lenses.

EXAMPLE 8

The basic lens data of Example 8 is shown below in Table 8.

TABLE 8 Example 8 in mm f = 6.913 Fno = 2.40 ω(°) = 41.4 ih = 5.992Surface Data Curvature Surface Refractive Abbe Surface No. i Radius rDistance d Index Nd Number vd (Object Surface) Infinity Infinity  1(Stop) Infinity −0.18  2* 4.294 1.184 1.5438 55.57  3* 200.000 0.471  4*−26.106 0.450 1.6142 25.58  5* 7.243 0.187  6* 6.633 0.813 1.5346 56.16 7* −49.555 0.704  8* −3.935 1.409 1.5346 56.16  9* −1.943 0.045 10*11.832 0.799 1.6142 25.58 11* 4.889 0.618 12* 6.063 1.239 1.5346 56.1613* 2.466 0.700 14 Infinity 0.300 1.5640 51.30 15 Infinity 0.997 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 28.053 2 4 −9.183 3 6 10.998 4 8 5.757 5 10 −14.186 6 12 −8.834 CompositeFocal Length f1234 5.02 f56 −5.05 Aspheric Surface Data 2nd Surface 3rdSurface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A4 −1.238E−03  −5.995E−03   −1.168E−02   −1.474E−02   −1.810E−02   −6.553E−03   A6−6.062E−04   −3.635E−03   −3.051E−03   2.514E−03 2.488E−03 4.182E−04 A81.726E−04 3.712E−04 9.538E−06 −6.658E−04   −4.442E−04   −1.100E−04   A10−1.519E−04   −2.456E−04   −2.696E−04   1.943E−05 4.679E−05 3.600E−05 A120.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A140.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A160.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 8th Surface9th Surface 10th Surface 11th Surface 12th Surface 13th Surface k0.000E+00 −2.589E+00   0.000E+00 0.000E+00 0.000E+00 −4.863E+00   A4−5.026E−03   −1.322E−02   4.201E−03 −4.963E−03   −1.318E−02  −7.355E−03   A6 3.086E−03 1.712E−03 −1.337E−03   −3.104E−04   4.018E−044.555E−04 A8 −4.218E−05   −7.045E−05   1.060E−04 2.256E−05 8.378E−06−2.390E−05   A10 −1.427E−05   5.363E−06 −6.562E−06   −1.036E−06  −8.208E−07   8.323E−07 A12 0.000E+00 1.730E−06 1.860E−07 2.383E−081.535E−08 −1.568E−08   A14 0.000E+00 −1.920E−07   0.000E+00 −7.919E−11  3.578E−10 1.173E−10 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00−1.367E−11   0.000E+00

As shown in Table 12, the imaging lens in Example 8 satisfies all theconditional expressions (1) to (14).

FIG. 16 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 8. As shown in FIG. 16,each aberration is corrected properly.

In addition, the imaging lens provides a wide field of view of about 80degrees and high brightness with an F-value of about 2.4. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.82,which suggests that it achieves compactness though it uses sixconstituent lenses.

EXAMPLE 9

The basic lens data of Example 9 is shown below in Table 9.

TABLE 9 Example 9 in mm f = 6.909 Fno = 2.41 ω(°) = 41.0 ih = 5.992Surface Data Curvature Surface Refractive Abbe Surface No. i Radius rDistance d Index Nd Number vd (Object Surface) Infinity Infinity  1(Stop) Infinity −0.23  2* 3.400 1.281 1.5438 55.57  3* −10.751 0.114  4*32.750 0.450 1.6349 23.97  5* 4.090 0.501  6* 10.920 0.716 1.5346 56.16 7* −105.924 0.501  8* −3.044 1.083 1.5346 56.16  9* −2.194 0.053 10*7.154 0.769 1.6142 25.58 11* 7.331 0.731 12* −21.180 1.000 1.5346 56.1613* 3.815 0.700 14 Infinity 0.300 1.5640 51.30 15 Infinity 0.603 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 24.906 2 4 −7.405 3 6 18.556 4 8 10.177 5 10 181.806 6 12 −5.963Composite Focal Length f1234 5.77 f56 −6.49 Aspheric Surface Data 2ndSurface 3rd Surface 4th Surface 5th Surface 6th Surface 7th Surface k0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A4−2.054E−03   7.097E−03 1.854E−03 −9.973E−03   −1.741E−02   −7.205E−03  A6 −1.032E−03   −6.396E−03   −3.369E−04   6.640E−03 1.031E−03−2.310E−04   A8 1.635E−04 −5.385E−04   −2.670E−03   −2.290E−03  −3.293E−04   −1.787E−04   A10 −1.975E−04   2.329E−04 6.838E−04 3.700E−041.826E−04 1.002E−04 A12 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 0.000E+00 A14 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 0.000E+00 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 0.000E+00 8th Surface 9th Surface 10th Surface 11th Surface12th Surface 13th Surface k 0.000E+00 −2.488E+00   0.000E+00 0.000E+000.000E+00 −1.000E+01   A4 1.689E−02 −8.823E−03   −1.043E−02  −6.524E−03   −9.314E−03   −8.578E−03   A6 1.595E−03 2.685E−03 3.311E−04−2.498E−04   5.346E−04 5.101E−04 A8 2.109E−05 9.872E−05 −4.170E−05  1.449E−05 6.335E−06 −2.015E−05   A10 −2.603E−05   −2.210E−05  −5.012E−06   −5.031E−07   −9.193E−07   4.062E−07 A12 0.000E+00−1.308E−06   4.209E−07 −5.571E−10   1.189E−08 −7.831E−09   A14 0.000E+008.363E−08 0.000E+00 1.274E−09 1.700E−10 1.639E−10 A16 0.000E+000.000E+00 0.000E+00 0.000E+00 −1.078E−12   0.000E+00

As shown in Table 12, the imaging lens in Example 9 satisfies all theconditional expressions (1) to (14).

FIG. 18 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 9. As shown in FIG. 18,each aberration is corrected properly.

In addition, the imaging lens provides a wide field of view of about 80degrees and high brightness with an F-value of about 2.4. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.73,which suggests that it achieves compactness though it uses sixconstituent lenses.

EXAMPLE 10

The basic lens data of Example 10 is shown below in Table 10.

TABLE 10 Example 10 in mm f = 6.913 Fno = 2.40 ω(°) = 41.4 ih = 5.992Surface Data Curvature Surface Refractive Abbe Surface No. i Radius rDistance d Index Nd Number vd (Object Surface) Infinity Infinity  1(Stop) Infinity −0.15  2* 5.000 1.092 1.5438 55.57  3* −12.801 0.288  4*33.017 0.450 1.6355 23.91  5* 5.658 0.491  6* 7.463 0.976 1.5346 56.16 7* 12.272 0.551  8* −4.977 1.342 1.5346 56.16  9* −1.810 0.045 10*−197.213 0.800 1.6142 25.58 11* 7.294 0.451 12* 5.257 1.150 1.5346 56.1613* 2.200 1.000 14 Infinity 0.300 1.5640 51.30 15 Infinity 0.809 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 26.758 2 4 −10.823 3 6 33.265 4 8 4.637 5 10 −11.435 6 12 −8.143Composite Focal Length f1234 4.64 f56 −4.33 Aspheric Surface Data 2ndSurface 3rd Surface 4th Surface 5th Surface 6th Surface 7th Surface k0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A4−4.597E−03   −5.555E−03   5.888E−06 −4.801E−03   −1.949E−02  −1.047E−02   A6 −1.478E−03   −2.588E−03   −9.844E−05   3.145E−032.205E−03 −2.179E−04   A8 1.482E−05 −3.202E−04   −1.061E−03  −1.060E−03   −3.529E−04   8.678E−05 A10 −1.200E−04   7.228E−05 2.393E−041.384E−04 5.625E−05 −8.720E−06   A12 0.000E+00 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 A14 0.000E+00 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 8th Surface 9th Surface 10th Surface 11thSurface 12th Surface 13th Surface k 0.000E+00 −2.653E+00   0.000E+000.000E+00 0.000E+00 −4.743E+00   A4 −7.814E−03   −1.277E−02   1.231E−021.336E−03 −1.520E−02   −8.717E−03   A6 2.935E−03 1.553E−03 −2.235E−03  −7.505E−04   8.498E−04 7.948E−04 A8 −2.505E−04   −4.834E−05   1.591E−043.660E−05 −6.573E−05   −7.230E−05   A10 8.593E−06 −7.511E−08  −9.556E−06   −1.218E−06   4.344E−06 4.070E−06 A12 0.000E+00 1.099E−062.849E−07 5.111E−08 −1.365E−07   −1.197E−07   A14 0.000E+00 −1.634E−08  0.000E+00 −1.095E−09   1.428E−09 1.422E−09 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 2.300E−12 0.000E+00

As shown in Table 12, the imaging lens in Example 10 satisfies all theconditional expressions (1) to (14).

FIG. 20 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 10. As shown in FIG. 20,each aberration is corrected properly.

In addition, the imaging lens provides a wide field of view of about 80degrees and high brightness with an F-value of about 2.4. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.80,which suggests that it achieves compactness though it uses sixconstituent lenses.

EXAMPLE 11

The basic lens data of Example 11 is shown below in Table 11.

TABLE 11 Example 11 in mm f = 5.759 Fno = 2.61 ω(°) = 45.7 ih = 5.992Surface Data Curvature Surface Refractive Abbe Surface No. i Radius rDistance d Index Nd Number vd (Object Surface) Infinity Infinity  1*3.645 0.565 1.5438 55.57  2* 18.893 0.032  3 (Stop) Infinity 0.514  4*68.525 0.390 1.6355 23.91  5* 6.299 0.130  6* 9.539 0.921 1.5346 56.16 7* −10.065 0.762  8* −2.630 1.024 1.5346 56.16  9* −1.586 0.030 10*7.455 0.700 1.6355 23.91 11* 4.517 0.414 12* 4.968 0.934 1.5346 56.1613* 2.042 1.000 14 Infinity 0.300 1.5640 51.30 15 Infinity 0.636 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 28.199 2 4 −10.952 3 6 9.313 4 8 5.570 5 10 −19.889 6 12 −7.298 CompositeFocal Length f1234 4.41 f56 −5.18 Aspheric Surface Data 1st Surface 2ndSurface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 A4 4.343E−05−3.910E−03   −1.396E−02   −9.859E−03   −8.799E−03   −4.773E−03   A6−2.066E−03   −3.476E−03   −6.107E−03   1.527E−03 2.118E−03 −1.361E−03  A8 1.401E−03 −7.714E−04   6.014E−04 −9.641E−04   1.897E−04 −1.950E−04  A10 −1.297E−03   −8.181E−04   −1.181E−03   6.941E−05 −9.219E−05  −4.487E−05   A12 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A14 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+000.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface13th Surface k 0.000E+00 −2.422E+00   0.000E+00 0.000E+00 0.000E+00−4.772E+00   A4 2.518E−03 −2.843E−02   −5.843E−03   −1.010E−02  −1.775E−02   −8.886E−03   A6 2.815E−03 5.152E−03 −2.899E−04  −1.417E−04   5.175E−04 4.875E−04 A8 1.128E−04 −4.842E−04   −7.986E−06  2.549E−05 5.221E−06 −2.013E−05   A10 −1.134E−04   7.897E−05 1.285E−06−1.525E−06   −3.995E−07   4.873E−07 A12 0.000E+00 −3.041E−06   1.488E−071.974E−08 7.138E−09 −7.890E−09   A14 0.000E+00 3.546E−08 −3.481E−08  −3.768E−10   −2.883E−10   9.866E−11 A16 0.000E+00 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00

As shown in Table 12, the imaging lens in Example 11 satisfies all theconditional expressions (1) to (14).

FIG. 22 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 11. As shown in FIG. 22,each aberration is corrected properly.

In addition, the imaging lens provides a wide field of view of about 90degrees and high brightness with an F-value of about 2.6. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.69,which suggests that it achieves compactness though it uses sixconstituent lenses.

As explained above, the imaging lenses according to the preferredembodiment of the present invention realize a high-resolution opticalsystem which provides a wide field of view of about 80 to 90 degrees andcorrects aberrations properly. In addition, the ratio of total tracklength TTL to maximum image height ih (TTL/2ih) is 0.85 or less,achieving compactness. They also provide high brightness with an F-valueof 2.2 to 2.6.

Table 12 shows data on Examples 1 to 11 in relation to the conditionalexpressions (1) to (14).

TABLE 12 Example Example Example Example Example Example Example ExampleExample Example Example 1 2 3 4 5 6 7 8 9 10 11 Conditional 0.71 0.780.79 0.81 0.82 0.81 0.86 1.16 0.71 0.98 1.42 Expression (1) 0.55 < f1/f< 1.5 Conditional −1.07 −1.14 −1.18 −1.20 −1.21 −1.33 −1.34 −1.33 −1.07−1.57 −1.90 Expression (2) −2.0 < f2/f < −0.9 Conditional 55.57 55.5755.57 55.57 55.57 55.57 55.57 55.57 55.57 55.57 55.57 Expression (3) 45< vd1 < 80 Conditional 25.58 25.58 25.58 25.58 25.58 23.97 23.97 25.5823.97 23.91 23.91 Expression (4) 20 < vd2 < 40 Conditional 56.16 56.1656.16 56.16 56.16 56.16 56.16 56.16 56.16 56.16 56.16 Expression (5) 50< vd3 < 75 Conditional 56.16 56.16 56.16 56.16 56.16 56.16 56.16 56.1656.16 56.16 56.16 Expression (6) 50 < vd4 < 75 Conditional 25.58 25.5825.58 25.58 25.58 23.97 23.97 25.58 25.58 25.58 23.91 Expression (7) 20< vd5 < 40 Conditional 56.16 56.16 56.16 56.16 56.16 56.16 56.16 56.1656.16 56.16 56.16 Expression (8) 50 < vd6 < 75 Conditional 0.86 0.820.82 0.82 0.81 0.82 0.76 0.81 0.82 0.79 0.78 Expression (9) 0.65 < Σd/TTL < 0.90 Conditional 1.26 1.35 1.35 1.35 1.34 1.38 1.39 1.42 1.27 1.391.43 Expression (10) TTL/f < 1.6 Conditional 0.89 0.89 0.89 0.89 0.870.89 0.88 0.87 0.87 0.87 1.04 Expression (11) 0.8 < ih/f < 1.2Conditional 5.83 3.31 3.36 3.51 2.27 3.69 2.78 1.59 2.69 4.81 1.62Expression (12) 1.3 < f3/f < 7.0 Conditional 6.29 2.53 2.51 2.44 2.310.74 0.72 0.73 0.84 0.67 0.77 Expression (13) 0.5 < f1234/f < 7.5Conditional −0.69 −0.76 −0.77 −0.84 −0.83 −0.72 −0.77 −0.73 −0.94 −0.63−0.90 Expression (14) −1.2 < f56/f < −0.5

The imaging lens composed of six constituent lenses according to thepresent invention features compactness and a wide field of view andmeets the demand for high resolution. In particular, when it is used ina highly functional product such as a smart TV or 4K TV, or aninformation terminal such as a game console or PC, or an increasinglycompact and low-profile mobile terminal such as a smart phone, mobilephone or PDA (Personal Digital Assistant), it enhances the performanceof the product in which it is mounted.

The effects of the present invention are as follows.

According to the present invention, it is possible to provide ahigh-brightness compact imaging lens which delivers higher opticalperformance than conventional imaging lenses when it is used not only ina conventional small image sensor but also in a large image sensor, andprovides a wide field of view and can correct various aberrationsproperly.

What is claimed is:
 1. An imaging lens for a solid-state image sensor,comprising in order from an object side to an image side of the imaginglens: a first lens having positive refractive power and a convex surfacefacing the object side; a second lens having negative refractive powerand a concave surface facing the image side; a third lens that is adouble-sided aspheric lens having positive refractive power and a convexsurface facing the object side; a fourth lens having positive refractivepower and a convex surface facing the image side; a fifth lens that is adouble-sided aspheric lens having a concave surface facing the imageside; and a sixth lens having negative refractive power and a concavesurface facing the image side, an image-side surface of the sixth lenshaving an aspheric shape with a pole-change point separated from anoptical axis of the imaging lens, wherein the maximum field of view ofthe imaging lens is 80 degrees or more.
 2. The imaging lens according toclaim 1, wherein when f is an overall focal length of the imaging lens,and ih is a maximum image height, a conditional expression (11b) belowis satisfied:0.87≦ih/f≦1.04  (11b).
 3. The imaging lens according to claim 1, whereinwhen TTL is a distance along the optical axis from an image plane of theimaging lens to an object-side surface of an optical element locatednearest an imaged object, and Σd is a distance along the optical axisfrom an object-side surface of the first lens to the image-side surfaceof the sixth lens, a conditional expression (9) below is satisfied:0.65<Σd/TTL<0.90  (9).
 4. The imaging lens according to claim 3, whereinwhen f is an overall focal length of the imaging lens, a conditionalexpression (10) below is satisfied:TTL/f<1.6  (10).
 5. The imaging lens according to claim 1, wherein: thefirst lens is a biconvex lens, the second lens is a meniscus lens, thefifth lens is a meniscus lens having negative refractive power and eachof an object-side surface and an image-side surface of the fifth lenshas an aspheric shape with a pole-change point separated from theoptical axis, and the sixth lens is a meniscus lens and an object-sidesurface of the sixth lens has an aspheric shape with a pole-change pointseparated from the optical axis.
 6. The imaging lens according to claim1, wherein when f is an overall focal length of the imaging lens, and f1is a focal length of the first lens, a conditional expression (1) belowis satisfied:0.55<f1/f<1.7  (1).
 7. The imaging lens according to claim 6, whereinwhen f2 is a focal length of the second lens, a conditional expression(2) below is satisfied:−2.3<f2/f<−0.8  (2).
 8. The imaging lens according to claim 7, whereinwhen f3 is a focal length of the third lens, a conditional expression(12) below is satisfied:1.3<f3/f<7.0  (12).
 9. The imaging lens according to claim 1, wherein,when νd1 is an Abbe number of the first lens at d-ray, and νd2 is anAbbe number of the second lens at d-ray, conditional expressions (3) and(4) below are satisfied:45<νd1<80  (3)20<νd2<40  (4).
 10. The imaging lens according to claim 1, wherein, whenνd3 is an Abbe number of the third lens at d-ray, νd4 is an Abbe numberof the fourth lens at d-ray, νd5 is an Abbe number of the fifth lens atd-ray, and νd6 is an Abbe number of the sixth lens at d-ray, conditionalexpressions (5) to (8) below are satisfied:50<νd3<75  (5)50<νd4<75  (6)20<νd5<40  (7)50<νd6<75  (8).
 11. An imaging lens for a solid-state image sensor,comprising, in order from an object side to an image side of the imaginglens: a first lens having positive refractive power and convex surfacesfacing the object side and the image side; a second lens having negativerefractive power, a convex surface facing the object side, and a concavesurface facing the image side; a third lens that is a double-sidedaspheric lens having positive refractive power and a convex surfacefacing the object side; a fourth lens having positive refractive powerand a convex surface facing the image side; a fifth lens that is adouble-sided aspheric lens having a concave surface facing the imageside; and a sixth lens that is a double-sided aspheric lens having aconcave surface facing the image side, an image-side surface of thesixth lens having an aspheric shape with a pole-change point separatedfrom an optical axis of the imaging lens, wherein a composite refractivepower of the fifth and sixth lenses is negative.
 12. The imaging lensaccording to claim 11, wherein when f is an overall focal length of theimaging lens, and ih is a maximum image height, a conditional expression(11) below is satisfied:0.8<ih/f<1.2  (11).
 13. The imaging lens according to claim 11, whereinwhen TTL is a distance along the optical axis from an image plane of theimaging lens to an object-side surface of an optical element locatednearest an imaged object, and Σd is a distance along the optical axisfrom an object-side surface of the first lens to the image-side surfaceof the sixth lens, a conditional expression (9) below is satisfied:0.65<Σd/TTL<0.90  (9).
 14. The imaging lens according to claim 13,wherein when f is an overall focal length of the imaging lens, aconditional expression (10) below is satisfied:TTL/f<1.6  (10).
 15. The imaging lens according to claim 11, wherein:the fifth lens is a meniscus lens having negative refractive power andeach of an object-side surface and an image-side surface of the fifthlens has an aspheric shape with a pole-change point separated from theoptical axis, and the sixth lens is a meniscus lens and an object-sidesurface of the sixth lens has an aspheric shape with a pole-change pointseparated from the optical axis.
 16. The imaging lens according to claim11, wherein when f is an overall focal length of the imaging lens, andf1 is a focal length of the first lens, a conditional expression (1)below is satisfied:0.55<f1/f<1.7  (1).
 17. The imaging lens according to claim 16, whereinwhen f2 is a focal length of the second lens, a conditional expression(2) below is satisfied:−2.3<f2/f<−0.8  (2).
 18. The imaging lens according to claim 17, whereinwhen f3 is a focal length of the third lens, a conditional expression(12) below is satisfied:1.3<f3/f<7.0  (12).
 19. The imaging lens according to claim 11, whereinwhen νd1 is an Abbe number of the first lens at d-ray, and νd2 is anAbbe number of the second lens at d-ray, conditional expressions (3) and(4) below are satisfied:45<νd1<80  (3)20<νd2<40  (4).
 20. The imaging lens according to claim 11, wherein whenνd3 is an Abbe number of the third lens at d-ray, νd4 is an Abbe numberof the fourth lens at d-ray, νd5 is an Abbe number of the fifth lens atd-ray, and νd6 is an Abbe number of the sixth lens at d-ray, conditionalexpressions (5) to (8) below are satisfied:50<νd3<75  (5)50<νd4<75  (6)20<νd5<40  (7)50<νd6<75  (8).